Jermaine Calver discusses how to achieve air quality without costing the earth and explains how Eurovent certification can help.
It is estimated that 85% of the costs produced by an air filter are energy costs accrued during operation, with just 15% of the expenditure relating to the upfront cost, maintenance and disposal of the filter.

The fact remains however that air filters are a necessary - indeed, a compulsory - requirement in air conditioning systems, and are particularly crucial in installations such as hospitals, laboratories and clean rooms.

This presents system designers with a challenge. How do you ensure that the clean air requirements are met without sacrificing sustainability?

This isn't just a hot topic for the system designer. It has been the subject of much debate at a European level in recent years and, in light of the latest developments, it should now be easier for system designers to identify the most effective combination of filtration performance and energy efficiency.

As with all Europe-wide initiatives however, you need to understand how the performance standards have been arrived at.

European standards
Air filters are divided into two categories - particle air filters and particulate air filters - and these categories are underpinned by two European standards.

EN779 covers coarse, medium and fine dust filters. Coarse dust filters, for particle sizes greater than 10µm, are covered by filter classes G1 to G4.

These would be expected to deal with particles such as insects, sand, textile fibres and pollen, and would typically be used in applications such domestic air conditioning systems and kitchen extractors.

EN779-2011 introduced two new medium filter classes, M5 and M6 to replace the previous grades (F5 and F6). These, along with F7, are for particle sizes between 1µm and 10µm. Typical applications for these could be factory buildings, retail outlets and so on.

The final filter grades covered by EN779 are F7 to F9. Suitable for particles such as oil spray or tobacco smoke, these would typically be used as final filters in air conditioning systems for offices, or as prefilters in environments requiring higher levels of protection.

The second European standard, EN1822, covers high efficiency air filters for critical environments and those governed by ISO standards. EN1822 covers particle sizes below 1µm and includes the E10 to E12 classes of efficient particulate air filters and the H13 class of high efficiency particulate air filters (HEPA).

These are typically employed in laboratories and in industrial settings requiring clean room standards.

Also encompassed by EN1822 are the H13 and H14 classes of HEPA filters and the U15 to U17 classes of ultra low penetration air filters. These are designed to meet the requirements of the various ISO standards.

Energy efficiency
Increasing the system resistance is, of course, an inevitable trade-off when employing particle or particulate filtration, so it is no surprise that the energy efficiency of filter designs has come under the spotlight in recent years.

In March 2007, the European Association of Air Handling on Refrigerating Manufacturers Equipment introduced a certification programme to cover all air filter elements of the classes F5 - F9 as covered by the EN779 standard.

It is one of 19 certification programmes run by Eurovent and aims to institute voluntary control of filter performance data with testing carried out by independent organisations. Currently there are fourteen manufacturers of filters taking part in the scheme, of which Trox is one.

The tests are carried out by independent organisations on an annual basis using products selected at random.

The data controlled includes performance of Class F5-F9 filters according to EN779 standard without Annex A - discharging by IPA - ÄP at nominal airflow rate, to tolerances ± (10 Pa ± 5 Pa) or ± (10 Pa ± 5 %) whichever is larger.

Participants have to provide and keep Eurovent updated with technical data of all their EN779 fine filter products.

This data is published at www.eurovent-certification.com and can be reviewed by customers.

After having successfully passed the tests, the product manufacturer is awarded a certification diploma and is published under Eurovent's home page.

If a product fails the participant has to change filter design, change brochure data or withdraw from the programme.

So, for the customer, there is an added level of confidence when selecting products which carry Eurovent certification.

So what are the grades and how can they assist when designing and specifying systems?

Eurovent grading
The Eurovent grading is based on the calculation of the average pressure drop of the filter.

From this the energy consumption is calculated and the product is given Eurovent certification against a specific grade using a simple A to G scale similar to that used for electrical appliances and in Energy Performance Certificates for homes.

For system designers, particularly those analysing life-cycle cost, this can be extremely useful to calculate the financial impact of various specification choices on the energy consumption of a final system.

As the certification programme allows complying products to display the Eurovent logo and classification, it can also make it much quicker and easier to identify products with superior performance.

Trox, for example, when designing its X-cube compact range of air handling units, decided to specify Eurovent-certified energy class A minipleat filters from the Trox range. X-cube Compact ready-to-use and pre-configured air handling units, for flow rates up to 1.7m3/sec, are high efficiency systems with a heat recovery performance of over 80%. Eurovent-certified filters, in addition to IE4 compliant EC motors, contribute to the units' outstanding energy efficiency.

At the same time, the effectiveness of the filters is one of a number of design features which help the units excel in terms of air quality and hygiene.
In summary, system designers continually try to balance the dual priorities of air quality and energy efficiency.

The latest Eurovent scheme introduces an additional Europe-wide layer of independent testing which can bring additional confidence and speed of selection for the specifier, and offers the site owner additional peace of mind.

// The author is commercial manager at Trox UK //